1. Field of the Invention
The present invention relates to a lead frame processing method and apparatus thereof which carries out the grease removal process, electrolytic process, deoxidizing process, plating process, etc., of the lined-up strip-shaped lead frames, on each of which a semiconductor chip is mounted and then sealed by a resin into a resin body.
2. Description of the Related Art
Ordinarily, semiconductor chips with their electronic circuits are mounted on their respective strip-shaped lead frames, and then sealed with a resin. Afterwards, they are subjected to various processes such as a deburring process, an electrolytic process, and a deoxidizing process. Unlike the lead frames on each of which a semiconductor chip, etc. is not mounted, these processes need adjustments to the conveying method, the soaking method in the processing reservoir, etc.
For example, the lead frame's surface processing apparatus disclosed in the Japanese Patent Application Laid-open No. Hei 5-275593 is comprised of an endless conveyer belt, which runs in the lengthwise direction of the electrolytic process reservoir, and hinges that are fixed to several areas of the belt and clamp the edges of the respective strip-shaped lead frames onto the belt. Wherein, at one end of the electrolytic process reservoir, the first guide is fixed so as to change the horizontal sideways posture of each hinge to a vertical downward posture, whereas the second guide is fixed to the other end of the reservoir, so as to change the vertical downward posture of each hinge to a horizontal sideways posture.
In this structure, when each hinge arrives at the first guide, it clasps the forwarded lead frame, which is then moved by the conveyer belt and switched from its horizontal sideways posture to a vertical downward posture by the first guide, and then soaked in the chemical fluid, which is in the electrolytic process reservoir. Afterwards, the conveyer belt conveys the vertical postures of lead frames into the electrolytic process reservoir; thus soaking them in the chemical fluid. They then pass between two electrode plates, which are arranged in their respective places, located away from the both sides of the running lead frame and at equal distances apart; so that both sides of each lead frame can be uniformly electrolyzed or plated.
However, there are the following problems with the conventional surface-processing of the lead frames. Since the fluid surface in the electrolytic process reservoir, which soaks the lead frames, is exposed to the air, the chemical fluid lies stagnant. This causes an occurrence of difference in density between the surface and the center of the fluid. As a result, the surface of each lead frame is partially uneven. Also, when used over a long period of time, active chemical fluid is lost, which causes changes in the quality of the processed lead frames.
Furthermore, when a breakdown occurs in the apparatus, there is the problem of having to manually remove the lead frames from the electrolytic process reservoir, which then must be cleaned by another cleaning apparatus. This wastes a great deal of work.